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| United States Patent |
6,191,055
|
|
Boyer, III
, et al.
|
February 20, 2001
|
Oil-tolerant reinforcement strip
Abstract
A diaper construction is provided with an external porous reinforcement
strip at the front part of the outside of the diaper, which strip provides
reinforcement against an adhesive fastening tab and provides an oil
contamination tolerant adhesion surface.
| Inventors:
|
Boyer, III; Charles E. (Oakdale, MN);
Kinney; Robert J. (Woodbury, MN);
Gobran; Ramsis (Roseville, MN);
Velasquez Urey; Ruben E. (St. Paul, MN);
Midgley; Roland R. (Minneapolis, MN)
|
| Assignee:
|
3M Innovative Properties Company (St. Paul, MN)
|
| Appl. No.:
|
181531 |
| Filed:
|
October 28, 1998 |
| Current U.S. Class: |
442/80; 428/99; 428/304.4; 428/315.5; 428/355EN; 604/385.01; 604/386; 604/389; 604/390 |
| Intern'l Class: |
A61F 013/58; B32B 027/04 |
| Field of Search: |
604/385.1,386,389,390
428/99,304.4,315.5,355
442/80
|
References Cited
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| 3991002 | Nov., 1976 | Sadlo.
| |
| 4237889 | Dec., 1980 | Gobran | 128/287.
|
| 4539256 | Sep., 1985 | Shipman | 428/315.
|
| 4861635 | Aug., 1989 | Carpenter et al.
| |
| 4902553 | Feb., 1990 | Hwang et al. | 428/156.
|
| 5019071 | May., 1991 | Bany et al. | 604/389.
|
| 5106383 | Apr., 1992 | Mulder et al. | 604/389.
|
| 5112889 | May., 1992 | Miller et al. | 524/77.
|
| 5264281 | Nov., 1993 | Arakawa et al. | 428/354.
|
| 5308695 | May., 1994 | Arakawa et al. | 428/354.
|
| 5468237 | Nov., 1995 | Miller et al.
| |
| 5562983 | Oct., 1996 | Kono et al.
| |
| 5885269 | Mar., 1999 | Boyer, III et al.
| |
| Foreign Patent Documents |
| 663894 | Apr., 1994 | AU.
| |
| 677912 | Nov., 1995 | AU.
| |
| 2221172 | Mar., 1994 | CA.
| |
| 0 291 984 | Nov., 1988 | EP | .
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| 0 306 232 | Mar., 1989 | EP | .
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| 0 375 862 B1 | Aug., 1994 | EP.
| |
| 0 661 959 B1 | Jul., 1995 | EP.
| |
| 106812 | Aug., 1993 | IL.
| |
| 54-145740 | Nov., 1979 | JP | .
|
| 58-149303 | Sep., 1983 | JP | .
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| 57-165978 | May., 1984 | JP | .
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| 59-228008 | Dec., 1984 | JP | .
|
| 62-282003 | Dec., 1987 | JP | .
|
| 63-161035 | Jul., 1988 | JP | .
|
| 63-309605 | Dec., 1988 | JP | .
|
| 1-162804 | Jun., 1989 | JP | .
|
| 9305407 | Jul., 1994 | MX.
| |
| 936070 | Aug., 1993 | SA.
| |
| WO 92/08763 | May., 1992 | WO | .
|
| WO 94/06387 | Mar., 1994 | WO.
| |
Primary Examiner: Morris; Terrel
Assistant Examiner: Singh; Arti R.
Attorney, Agent or Firm: Griswold; Gary L., Sprague; Robert W., Bond; William J.
Parent Case Text
This is a division of application Ser. No. 08/769,064 filed Dec. 18, 1996
now U.S. Pat. No. 5,885,269 Mar. 23, 1999.
Claims
We claim:
1. A disposable garment is provided with a thin liquid-impermeable sheet
material and a pressure-sensitive adhesive closure system having at least
one attachment region on the thin sheet material having an outer surface
and a pressure-sensitive adhesive fastening tab having a free end to
adhere to said at least one attachment region outer surface and a second
opposite end permanently attached to a first edge region of the garment,
said at least one attachment region provided adjacent a second edge region
of said garment and having a polyolefin outer surface, said free end
pressure-sensitive adhesive comprising:
100 parts of a block copolymer elastomer formed of polyisoprene and
polystyrene blocks with at least 40 percent by weight
polyisoprene-polystyrene di-block copolymer said elastomer having a total
percent styrene content of at least 13 percent;
30 to 200 parts of an isoprene block compatible solid tackifier; and
0 to 15 percent by weight of a liquid resin or plasticizing oil,
wherein when said free end pressure-sensitive adhesive is applied to said
at least one attachment region, the pressure-sensitive adhesive fastening
tab is capable of providing a 135 degree peel using a 100 gm rolldown of
at least 30 N/m, with the attachment region having from 0 to 0.12
mg/cm.sup.2 of mineral oil on its polyolefin outer face.
2. The disposable garment of claim 1 wherein said pressure-sensitive
adhesive comprises 0-15 percent by weight plasticizing oil or liquid
tackifier, and the solid tackifier is a C.sub.5 resin, a C.sub.9 resin, a
beta-pinene resin or a rosin ester.
3. The disposable garment of claim 2 wherein said pressure-sensitive
adhesive polyisoprene-polystyrene elastomer has a percent styrene content
of 15-30 percent.
4. The disposable garment of claim 2 wherein said pressure-sensitive
adhesive comprises at least 60 percent diblock copolymer having a percent
styrene content of at least 20 percent, and the solid tackifier comprises
a C5 tackifier or beta-pinene resin.
5. The disposable garment of claim 3 wherein the at least one attachment
region outer surface comprises polyethylene.
6. The disposable garment of claim 5 wherein the said at least one
attachment region comprises a reinforcement zone provided by a plastic
strip or tape on the inner or outer face of the thin liquid-impermeable
sheet material.
7. The disposable garment of claim 5 wherein the at least one attachment
region is provided by a polyethylene plastic strip on the outer face of
the thin liquid-impermeable sheet material.
8. The disposable garment of claim 4 wherein the elastomer contains 65-85
weight percent diblock having a percent styrene content of 22-26 percent,
and the adhesive comprises 40 to 120 parts solid tackifier.
Description
BACKGROUND AND FIELD OF THE INVENTION
The present invention relates to improved disposable articles such as
diapers, incontinent products, disposable garments, feminine hygiene
products, and the like.
Disposable baby diapers are often used in conjunction with powders or oils
applied by the parent onto the baby. Quite often, the powder or oil
contaminates the outer backsheet portion of the diaper. Typically, the
powder or oil is transferred to the diaper backsheet by the parent's hands
or from the baby. A persistent problem with such powder and oil
contamination is that conventional adhesive tab closures used with diapers
are adhered onto the outer backsheet portion of the diaper and do not
adequately adhere to surfaces contaminated with talc or particularly oil.
U.S. Pat. No. 4,163,077 proposes a diaper closure system wherein the
adhesive used on the fastening tab is a particular blend of a synthetic
block copolymer and a blend of solid and liquid polyterpene type
tackifiers. This adhesive provides a limited ability to adhere to talc or
powder contaminated diaper surfaces, such as polyethylene backsheets
typically employed in commercial diaper constructions. However, this
adhesive composition does not address the problems of adhering to an
oil-contaminated diaper substrate.
The problem of adhering to oil-contaminated surfaces with conventional
pressure-sensitive adhesives is addressed in U.S. Pat. No. 3,991,002,
which describes a method for improving the adhesion of normal
pressure-sensitive adhesive tapes to oily or greasy substrates by treating
the oil-contaminated substrate with a primer. This primer comprises a
rubbery phase of a A-B-A triblock copolymer, such as a styrene-butadiene
or styrene-isoprene block copolymer, and a resin phase comprised of a
resin compatible with the conjugated diene portion of the block copolymer
and a resin compatible with the monovinyl aromatic hydrocarbon portion of
the block copolymer (i.e., styrene). These components are placed in a
solution, then applied as an aerosol to render the oil-contaminated
surface stable for subsequent adhesion. This patent states that the
conventional approach to adhering to oil-contaminated surfaces is a
complicated and time-consuming clean-up procedure. However, the primer
solution proposed in this patent is still impractical for most consumer
applications and particularly in a diaper being applied to a baby.
The present invention is addressed at solving the problems identified
above. Particularly, the invention is directed at providing a diaper
construction provided with a reinforced tape adhesion zone that has the
property of oil-contamination tolerance.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides a disposable garment, generally a diaper,
comprising an adhesive fastening tab permanently adhered to one corner of
the garment at first end of the tab. A second free end of the adhesive
fastening tab is provided to adhere to a reinforced outer surface of the
garment to effect closure of the garment by connecting the first-mentioned
corner to the reinforced surface by the two adhered ends of the fastening
tab. The reinforcement is provided by a reinforcing film or web layer
bonded to a thin outer film or web layer of the garment. The reinforcing
layer is comprised of a porous film or web wherein the pores preferably
contain at least a minor proportion of an incompatible oil or liquid
polymer, the porous reinforcement layer providing oil-contamination
tolerance, as well as reinforcing the thin outer film against tearing by
the removal of the free end of the adhesive fastening tab.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 represents a conventional diaper construction using the invention
microporous reinforcement layer as it would look when placed on a wearer.
DETAILED DESCRIPTION OF THE INVENTION
The invention oil-contamination tolerant adhesive closure system will be
described with reference to a conventional baby diaper, however, such a
closure system could be used in other applications using the adhesive
fastening tabs, such as adult incontinent garments, disposable medical
gowns, caps, packaging systems, feminine hygiene articles, and the like.
A conventional diaper construction is depicted in FIG. 1. The diaper 10 is
provided with a thin liquid-impermeable outer backsheet 2 and a
liquid-permeable inner cover sheet 3. Between the backsheet 2 and inner
coversheet 3 is an absorbent core (not shown). Adhesive fastening tabs 4
are provided at two laterally opposed side edge regions 7 at a first end
of the diaper. At a second end of the diaper on the backsheet 2 is
provided a porous reinforcement layer 11 of the invention. This porous
reinforcement layer 11 is permanently bonded to the outside face of the
thin diaper backsheet 2 providing a surface to which the free ends 12 of
the fastening tab 4 can be adhered. The porous reinforcement layer is
likewise located adjacent an edge region 7 so that when the free end 12 of
the fastening tab 4 is adhered to the porous reinforcing layer, two edge
regions 7 will overlap to effect closure of the diaper undergarment. The
porous reinforcement layer then exhibits the ability to provide a suitable
surface for adhering a fastening tab free end 12 under normal use
conditions, and when the reinforcement layer 11 is contaminated with oil.
When the free end 12 of the fastening tab 4 is attached to the porous
reinforcement layer 11, there is formed a leg opening 5, which is
typically provided with elastic means to form a sealing engagement with
the wearer's legs. The diaper may also be elasticated around the waist
portion to further provide sealing engagement with the wearer by
elasticated portions 6. Prior to use, the adhesive surface on the free end
12 of the adhesive fastening tab 4 is protected from contamination by a
release-coated paper or a release-coated tape, which can be provided on
the corners 7 of the inner top sheet 3. The backsheet 2 is typically a
thin polyethylene film, while the top sheet 3 would typically be a
nonwoven such as a spunbond polypropylene. The porous reinforcement layer
11 is attached to the backsheet film by conventional means, which would
include the use of hot-melt adhesives.
The reinforcement layer 11 can be a single strip or multiple strips (e.g.,
one for each fastening tab free end 12). The strip(s) should be provided
so that they cover the likely areas where the fastening tab free end 12
would be adhered in normal use.
Oil-contamination tolerance is provided by a porous reinforcement layer
having an affinity to oil, but providing a structurally coherent surface.
A coherent surface is one that will not delaminate or lose fibers (for a
web) when the adhesive tab free end 12 is removed therefrom. Such a porous
layer is generally characterized as one having an effective pore size of
20 microns or less, and is preferably a microporous film or web having an
effective pore size of 10 microns or less, preferably 1 micron or less.
Preferably, the pores will be interconnected. However, some oil tolerance
can be provided by layers with unconnected pores such as films with a
large number of punched small holes or a microporous film formed with a
large number of unconnected small pores.
The porous reinforcement layer 11 may be a microporous film or coherent
nonwoven web (one having an effective pore size of about 10 microns or
less, preferably less than 1 micron) and is preferably a film such as is
disclosed in U.S. Pat. Nos. 4,902,553, 4,539,256, 4,609,584, 4,726,989 or
4,824,719. The material described in these patents comprises a microporous
film formed by dissolving a crystallizable polymeric material in a liquid
additive at a temperature above the melt temperature of the polymeric
material and forming this melt into a film, such as by extrusion. The
homogeneous solution is then permitted to cool at a rate suitable to cause
the crystallizable polymer to crystallize into a distinct interconnected
phase, the polymer being incompatible with the additive at ambient or use
conditions. The phase-distinct film material is then uniaxially or
multiaxially orientated, creating a film with micropores, which pores
contain the now phase-distinct liquid additive. The liquid additive is
preferably one which exhibits plasticizing properties or affinity to the
adhesive on the free end of the fastening tab. Potential additive
materials include saturated hydrocarbons such as mineral oil, glycerin,
petroleum jelly, low molecular weight polyethylene, polyethylene oxide,
polypropylene oxide, polytetramethylene oxide, soft carbowax, plasticizing
oils, and the like. Preferred additive materials are plasticizing oils,
with mineral oil being particularly preferred because of its relatively
low cost and excellent film-forming properties. The crystallizable
polymeric material is preferably olefinic, such as polyolefins, or
condensation polymers such as polyesters or polyamides. Most preferred are
polyolefins such as crystalline isotactic polypropylene, polyethylene,
polybutylene, polyethylpentene, copolymers, block polymers and modified
versions thereof.
The additive liquid can be used in an amount ranging from about 5 to 80
percent by weight of the formed film, preferably 5 to 50 percent, and most
preferably 10 to 30 percent.
Discussions of crystallizable polymers and phase-separating additives are
also found in U.S. Pat. No. 4,247,498 and U.S. Pat. No. 4,100,238. For
example, for isotactic polypropylene, these patents describe, the use of
phase-separable additives such as poly-1-butene, polyethylene wax, low
molecular weight polyethylene, alcohols, aldehydes, amines, esters such as
methylene benzoate, ethers such as diphenylether, hydrocarbons such as
trans-stilbene or ketones.
Nucleating agents such as those described in U.S. Pat. Nos. 4,824,718 and
4,726,989 can also be used to produce uniform crystallization of the
polymeric material upon cooling. These nucleating agents preferably are at
least a primary agent, generally an organic acid or derivative, which
dissolves in the liquid additive at a temperature at least more than
10.degree. C. above the crystalline transition temperature of the
thermoplastic polymer, and which is used in amounts from 0.05 to 5 percent
by weight of the system, and optionally a secondary inert nucleating
agent, which is employed in approximately the same concentration. The
secondary inert nucleating agent normally comprises an inorganic
particulate material such as talc, titanium dioxide, calcium carbonate,
magnesium carbonate, barium carbonate, magnesium sulfide, barium sulfide,
and the like. Suitable organic acids include mono- or polyacids, e.g.
carboxylic acids, sulfonic acids, phosphonic acids, and solid organic
alcohols such as dibenzylidene sorbitol. The preferred organic acids
include adipic acid and succinic acid, and a preferred secondary
nucleating agent is talc.
Following precipitation of the thermoplastic crystallizable polymer, the
film can be used unoriented or preferably orientated with a stretch ratio,
in at least one direction, of 0 to 3, preferably from 1.5 to 2.5. When the
film is not oriented, the liquid additive is preferably washed from the
film.
Generally, the thickness of the microporous reinforcement sheet is from 5
to 250 microns, preferably from 30 to 200 microns. Comparatively thinner
films are preferred in terms of cost and increased moisture vapor
permeability where employed for this additional purpose. However, too thin
a film may be inadequate in providing an adequate level of reinforcement
to prevent the diaper backsheet from tearing. Thicker films provide
improved tensile performance and reinforcement against more aggressive
adhesives.
Moisture vapor permeability for the, e.g., diaper can be provided by
providing holes in the diaper backsheet material 2 behind a microporous
reinforcement layer 11. Generally, significant amounts of moisture vapor
permeability can be provided even where the holes are quite small, such as
pinholes, provided they are provided over a significant portion (e.g.,
greater than 2 percent open area, preferably greater than 5 percent) of
the backsheet film covered by the microporous reinforcement layer. Porous,
liquid-permeable (an effective pore size of greater than 1 micron) porous
reinforcement layers can also be used in this arrangement, however, are
not preferred as they can result in wetting of the wearer's garments.
Alternative porous reinforcement layers include microporous films, without
liquid additive, films rendered porous by mechanical means or highly
consolidated nonwovens. The microporous films are typically rendered
porous by blending in solid particulates, incompatible with the film
forming polymer, and then orienting the particulate containing film to
create pores. Examples of suitable particulates include calcium carbonate,
magnesium carbonate, calcium sulfate, and barium sulfate. The particulates
can be present in amounts ranging from about 5 to 80 weight percent,
preferably 40 to 70 weight percent of the film. The particle size range
can be from about 0.1 to 250 micrometers. At low particle loading levels
(e.g., around 5-20 weight percent) the films do not have the preferred
levels of porosity and connected pore structure desirable for higher
levels of oil-contamination tolerance. Other suitable particulate fillers
include talc, clay, silica, diatomaceous earth, alumina, mica, glass
powder, asbestos powder, zeolites, zinc oxide, magnesium oxide or organic
fillers such as polysiloxanes, or other incompatible polymers or starch or
cellulose powder, such as cellulose acetate, provided that the softening
point is higher than that of the film forming polymer.
It is also possible to produce non-liquid additive-containing microporous
films (porous films which do not contain liquid additive) by removing the
liquid additive from the liquid additive-containing porous films with a
suitable solvent selective to the liquid additive. Various other known
methods for producing microporous films or webs, such as cold stretching
of crystalline film forming polymers, are also suitable for forming
non-liquid additive containing microporous films.
The pressure-sensitive adhesive on the free end of the fastening tab is
preferably a tackified elastomer where the elastomer is an A-B type block
copolymer, wherein the A blocks and the B blocks are configured in linear,
radial, or star configurations. The A block is mono alkenyl arene,
preferably polystyrene, having a molecular weight between 4,000 and
50,000, preferably between 7,000 and 30,000. The A block content is
preferably about 10 to 50 percent, more preferably between 10 and 30
percent. Other suitable A blocks may be formed from alpha methyl styrene,
t-butyl styrene and other ring alkylated styrenes, as well as mixtures
thereof. The B block is an elastomeric conjugated diene, having an average
molecular weight from about 5,000 to about 500,000, preferably from about
50,000 to about 200,000. The elastomer preferably comprises at least 15
weight percent, more preferably 25 weight percent, of either block
copolymers having B end blocks, such as A-B diblock copolymers, or pure B
elastomer, most preferred are A-B block copolymers having B end blocks.
The presence of these B block terminated elastomers is preferred in that
pressure-sensitive adhesives employing elastomers containing these B block
terminated species generally display higher levels of tack to the liquid
additive-containing (particularly where the liquid additive is compatible
with the elastomeric B block) microporous reinforcement film (both when
contaminated with oil and not contaminated with oil), and generally
relatively lower levels of tack to the non-liquid additive-containing
porous polyethylene films. The non-liquid additive-containing porous films
often displayed non-functionally high levels of adhesion (e.g., 135 degree
peel values in excess of 1,200 gm/in) to pressure-sensitive adhesives with
predominately all A block terminated elastomer species. Further, block
copolymers having predominately A block end blocks provide adhesives which
have a tendency to lose substantially all adhesive properties when in
prolonged contact with the liquid additive-containing microporous film,
particularly where the liquid additive is compatible with the B block,
such as a mineral oil liquid additive.
The tackifying components for the elastomer-based adhesives generally
comprise solid tackifying resin used alone or in combination with a liquid
tackifying resin and/or a liquid plasticizer. Preferably, the tackifying
resin is selected from the group of resins at least partially compatible
with the diene B portion of the elastomeric polymer or block copolymer.
Such tackifying resins include those aliphatic hydrocarbon resins made
from the polymerization of a feed stream consisting mainly of unsaturated
species containing 4 to 6 carbon atoms; rosin esters and rosin acids;
mixed aliphatic/aromatic tackifying resins; polyterpene tackifers; and
hydrogenated tackifying resins. The hydrogenated resins can include resins
made from the polymerization and subsequent hydrogenation of a feed stock
consisting mainly of dicyclopentadiene; resins produced from the
polymerization and subsequent hydrogenization of pure aromatic feed
stocks, such as styrene; resins produced from the polymerization and
subsequent hydrogenation of an unsaturated aromatic feed stream, wherein
the feed stream consists mainly of species containing 7 to 10 carbon
atoms; hydrogenated polyterpene resins; and hydrogenated aliphatic and/or
aliphatic/aromatic resins. Preferred tackifying resins include the
aliphatic hydrocarbon resins and the hydrogenated resins. Although not
preferred, generally, a relatively minor portion of the tackifying resin
can include resins compatible with the A block, when present, generally
termed endblock reinforcing resins. Generally, these endblock resins are
formed from aromatic species.
Suitable liquid plasticizers for use in the fastening tab adhesive
composition include naphthenic oils, paraffinic oils, aromatic oils and
mineral oils.
Generally, higher composite glass transition temperature adhesives (e.g.,
above 250 Kelvin) show a better ability to adhere to the liquid
additive-containing microporous films, both uncontaminated and
contaminated with oil in amounts of up to 0.1 to 0.2 milligrams per square
centimeter.
The tackifing portion of the pressure-sensitive adhesive generally
comprises from 20 to 300 parts per 100 parts of the elastomeric phase.
Preferably, this is predominantly solid tackifier, however, from 0 to 20
weight percent, preferably 0 to 10 weight percent for adhesion to
polyethylene surfaces, of the adhesive can be liquid tackifier and/or
plasticizer.
Other conventional pressure-sensitive adhesives can be used with the
preferred liquid additive-containing porous films or non-liquid
additive-containing porous films such as acrylate-based adhesives or
adhesives based on other diene or non-diene elastomers or natural rubber.
The closure adhesive fastening tabs, when adhered to the reinforcement
layer(s) or film(s), preferably have 135.degree. peel adhesion of less
than about 1000 grams per inch, more preferably less than about 800 grams
per inch. At adhesions levels above this, the tape is difficult to remove
by the end user and risks tearing, e.g., the diaper. Generally, the
minimum acceptable 135.degree. peel is approximately 50 grams per inch,
and preferably greater than 80 grams per inch.
The liquid additive-containing film is preferred in that the initial
adhesion to the non-oil-contaminated reinforcement surface is generally
more comparable (and less likely to be excessively high) to the initial
adhesion to the oil-contaminated reinforcement surface with a broad range
of the above-described pressure-sensitive adhesives, providing a closure
with more consistent performance characteristics. Without wishing to be
bound by theory, it is believed that the liquid additive-containing
reinforcement film system functions by the liquid additive moderating the
adhesion levels of the adhesive when the reinforcement strip is not
contaminated with oil, while also rapidly removing surface oil from the
surface when contaminated.
The porous reinforcement layer has a generally opaque appearance caused by
the pore structure. Certain hot-melt adhesives used to apply microporous
film can cause the film to become transparent or translucent.
Consequently, with these adhesives, it is preferred that the reinforcement
layer or film be applied with a full coating of the adhesive for uniform
appearance purposes. Certain fastening tab adhesives will also have a
tendency to clarify a porous layer or film, which would provide an
indication of a suitable location to re-apply the tape tab after opening.
The following examples are the currently contemplated preferred modes for
carrying out the invention and should not be considered as limiting
thereof unless otherwise indicated in the examples.
EXAMPLES
The following tests were used to evaluate the porous reinforcement film.
135 Degree Peel Adhesion
This test is a modified version of PSTC-5. The test was carried out at
constant temperature and humidity (21.degree. C. and 50% relative
humidity) using a constant rate Instron.TM. tensile tester. The film
sample to be tested was securely adhered to a 2 in.times.5 in (5.1
cm.times.12.7 cm) steel panel using a double-coated adhesive tape. Within
10-60 minutes after securing the film sample to the steel panel a 1 in
(2.54 cm) wide strip of test tape was then placed adhesive side down onto
the film substrate and was rolled down onto the film substrate using two
passes of a 4.5 lb (2000 gm) hard rubber roller. The peel rate was 12
inches (30.5 cm) per minute. The force required to remove the fastening
tape from the test substrate is reported in the Tables in grams/inch.
Reported values are averages of at least two tests.
Shear Adhesion
The shear adhesion was measured by determining the length of time it took
for a 1 in.times.1 in (2.5 cm.times.2.5 cm) sample of test tape to shear
off of a film test substrate under a 1 kilogram load. A 2 in.times.6 in
(5.1 cm.times.15.2 cm) piece of the film substrate was laminated to a 2
in.times.6 in (5.1 cm.times.15.2 cm) piece of reinforcing tape (3M Y-9377)
in order to enhance the stiffness of the substrate. On the side opposite
the reinforcing tape, a 1 in.times.2 in (2.5 cm.times.5.1 cm) area of the
test tape was rolled down onto the film substrate using two passes of a
4.5 lb (2000 gm) hard rubber roller. The overlap area between the test
tape and the film substrate was 1 in.times.1 in (2.5 cm.times.2.5 cm). The
laminated substrate and the test tape were hung vertically in a 40.degree.
C. oven for 15 minutes after which a 1 kilogram weight was hung from the
test tape, generating a shear load at a 180.degree. angle. The time that
it took in minutes for the weight to drop was recorded as a measure of the
shear adhesion. Reported values are averages of 5 tests.
Oil-Contamination Test--135 Peel Adhesion from Loose Film and
Oil-Contaminated Film
Test panels consisted of 2 in.times.5 in (5.1 cm.times.12.7 cm) clean steel
panels which have had a strip of 0.75 in (1.9 cm) double-coated adhesive
affixed along each 2 in (5.1 cm) cross-direction edge. A sheet of the film
test substrate was laid down loosely over the test panel so that it was
flat without any wrinkles. The cross-direction of the film substrate was
parallel to the long dimension of the test panel. The film was rolled down
firmly onto the double-coated adhesive and any excess film that extended
beyond the edge of the test panel was trimmed away.
The film substrate side of the test panel was contaminated for testing by
uniform spray application of a known amount of baby oil onto the panels.
The amount of oil deposited was determined by weighing a set of panels
before and after spraying and was generally approximately 0.12
mg/cm.sup.2. Each sprayed panel was tested within 2 to 4 minutes of
completion of oil spraying. Additional panels for comparison were prepared
for testing as described above, but were not oil sprayed.
Each strip of test tape measured 1 in.times.2.5 in (2.5 cm.times.6.5 cm)
with a paper leader measuring 1 in.times.8 in (2.5 cm.times.20.3 cm)
adhered to the final 0.25 in (0.6 cm) of the tape. This tape assembly was
laid with its long dimension parallel to the long dimension of the panel
so that the tape was about equidistant from each cross-direction edge of
the panel and centered between each longitudinal side edge. No additional
pressure was exerted in laying down the tape. The tape was immediately
rolled down at 12 inches (30.5 cm) per minute with a single pass of a 100
gm rubber roller and was tested within 15 seconds of completion of
rolldown.
An Instron.TM. tensile tester was used for peel testing the samples. The
samples were tested at an angle of 135 degrees throughout the peel at a
constant crosshead speed of 12 inches (30.5 cm) per minute. The average
peel of each test specimen is reported in the Tables in grams/inch as a
measure of the peel adhesion value. The reported values are an average of
four tests. The minimum acceptable peel adhesion value for this test is
about 30 N/m (about 80 gm/in) for the oil-contaminated films, (i.e., with
an oil-contamination level of about 0.12 mg/cm.sup.2). Using the same test
procedure, tape peeled from a non-contaminated surface should have a
minimum peel adhesion value of about 40 N/m about 100 gm/in). The results
were reported in gm/in.
In the examples, the pressure-sensitive adhesives for fastening tapes 1-9
were formulated from the following materials.
Kraton.TM. 1107 is a polystyrene-polyisoprene linear block copolymer
available from Shell Chemical Co., having approximately 14-18% diblock and
80-85% triblock, a styrene content of approximately 14%, and a midblock Tg
of about 215 Kelvin.
Kraton.TM. 1111 is a polystyrene-polyisoprene linear block copolymer
available from Shell Chemical Co., having approximately 14-18% diblock and
80-85% triblock, a styrene content of approximately 22%, and a midblock Tg
of about 215 Kelvin.
Kraton.TM. 1112 is a polystyrene-polyisoprene linear block copolymer
available from Shell Chemical Co., having approximately 40% diblock and
60% triblock, a styrene content of approximately 14%, and a midblock Tg of
about 215 Kelvin.
Kraton.TM. RP-6411 is a polystyrene-polyisoprene linear block copolymer
available from Shell Chemical Co., having approximately 64% diblock and
36% triblock, and a styrene content of approximately 22%.
Cariflex.TM. IR-309 is a polyisoprene elastomer available from Shell
Chemical Co. having a number average molecular weight of 390,000, and a Tg
of 215 Kelvin.
Wingtack.TM. 95 is a solid C.sub.5 tackifying resin with a Tg of 323 Kelvin
available from Goodyear Chemical Co.
Wingtack.TM. Plus is a solid C.sub.5 tackifying resin with a Tg of 315
Kelvin available from Goodyear Chemical Co.
Escorez.TM. 1310 LC is a solid C.sub.5 tackifying resin with a Tg of 313.5
Kelvin available from Exxon Chemical Corp.
Shellflex.TM. 371 is a naphthenic oil having about 10% aromatics as
measured by clay-gel analysis having a Tg of 209 Kelvin and is available
from Shell Chemical Co.
Zonarez.TM. A-25 is a liquid alpha-pinene tackifying resin with a Tg of 251
Kelvin available from Arizona Chemical Co.
Irganox.TM. 1076 is a hindered phenol antioxidant available from
Ciba-Geigy.
The block copolymers used for fastening tapes 7 and 8 were admixtures of
pure polystyrene-polyisoprene (S-I) diblock copolymer and
polystyrene-polyisoprene-polystyrene (S-I-S) triblock copolymer
(.gtoreq.87% triblock) having the total percent diblock as indicated in
Table I, the remaining fraction being essentially triblock.
Fastening tapes 1-9 were prepared by either solvent coating or hot melt
coating each pressure-sensitive adhesive composition onto a polypropylene
(polypropylene/polyethylene polymer blend for fastening tapes 5 & 6) film
backing (backing thickness=approx. 4 mil). The pressure-sensitive adhesive
compositions (in parts by weight) and adhesive coating thicknesses are
given in Table I.
TABLE I
1 2 3 4 5 6 7 8 9
Kraton .TM. 1107 33.5
Kraton .TM. 1111 38.5
Kraton .TM. 1112 52 52
29.6
Kraton .TM. RP-6411 50 50
75/25 (S-I/S-I-S) 61.7
25% styrene
77/23 (S-I/S-I-S) 58
25% styrene
Cariflex .TM. IR-309
27.4
Wingtack .TM. 95 36.4 40.3
Wingtack .TM. Plus 46.4 38 38 37.5 38.5
41.4
Escorez .TM. 1310 46.5
Shellflex .TM. 371 15.1 10 10 12.5 10.5
1.6
Zonarez .TM. A-25 19
Irganox .TM. 1076 1 1 1 1 1 1 1.9 1.7
1
(100) (101) (101) (101) (101) (100) (100) (100)
(101)
Adhesive 50 38 50 21 38 38 32 32
42
thickness
(microns)
Coating Method Hot Sol- Hot Hot Hot Sol- Sol- Sol-
Sol-
melt vent melt melt melt vent vent vent
vent
EXAMPLES
Examples 1-27
Oil-filled polypropylene microporous films (15-35% oil) were prepared as
described in U.S. Pat. Nos. 4,539,256 and 4,726,989 stretched by a ratio
fo 1.6:1 in one direction. The oil was mineral oil (Amoco White mineral
oil #31 available from Amoco Oil Co.). Fastening tapes 1-9 were tested
against the microporous film samples for 1350 peel adhesion (using both
tests described), shear adhesion, and for oil-contamination tolerance. The
results are given in Table II. In Table II the microporous film samples
are defined as A=35% oil, 1.7 mil caliper, B=30% oil, 1.7 mil caliper,
C=25% oil, 1.3 mil caliper, D=20% oil, 1.2 mil caliper, and E=15% oil, 1.3
mil caliper. The effective pore size (measured using ASTM F-316-86) of
film A was 0.2 microns, and the effective pore size of film C was 0.16
microns.
TABLE II
135.degree. Peel 135.degree.
Peel
Porous Fastening (2000 gm 135.degree. Peel (loose)
Ex. Film Tape rolldown) Shear (loose) w/oil
1 A 1 433 10
2 B 1 595 7
3 C 1 871 47 156 76
4 D 1 1076 76
5 E 1 1474 184
6 A 2 589 1400+
7 C 2 506 1400+ 297 127
8 D 2 575 1400+
9 C 3 480 269 121
10 A 4 562 1320
11 C 4 425 1400+ 99 60
12 D 4 431 1400+
13 A 5 766 1400+ 157 95
14 B 5 234 145
15 C 5 720 1400+ 355 175
16 D 5 728 1400+ 523 278
scs
17 E 5 590 341
18 A 6 887 1400+ 193 113
19 C 6 731 1400+ 416 213
20 D 6 750 1400+
21 A 7 1049 1400+ 145 83
22 C 7 1040 1400+ 306 166
23 D 7 1014 1400+
24 A 8 1049 1400+ 166 101
25 C 8 1179 1400+ 362 209
26 D 8 1105 1400+
scs
27 C 9 555 225 131
scs = slight cohesive slippage
The oil-filled microporous films provided functional 135 degree peel
performance against all tapes tested both when contaminated with oil and
without oil. The shear performance of tape sample 1 was not acceptable
except against the low oil-containing microporous films. Generally,
superior peel performance was noted for the tapes having adhesives with a
relatively high percent of elastomeric (polyisoprene) end blocks, as A-B
diblock copolymers (tapes 3-8), with the possible exception of tape 4,
which is attributable to the very low coating weight of the adhesive for
that tape. The best peel performance was generally obtained for the lower
percent oil-containing films, less than about 30 percent oil.
Examples 28 and 29
Fastening tapes 1 and 5 were tested against a particle-filled (calcium
carbonate) 1.4 mil thick polyethylene microporous film. The microporous
film had a Gurley Value of 900 sec/50 cc (measured by ASTM-D-726-58,
method A). Results are given in Table III.
TABLE III
135.degree. Peel 135.degree. Peel
(2000 gm 135.degree. Peel (loose)
Ex. Tape rolldown) Shear (loose) w/oil
28 1 482 92
29 5 603 204
This film is believed to contain a low amount of process oil. Peel
performance for this film, when contaminated with oil, was excellent
(Example 29).
Example 30 and 31
Fastening tapes 1-9 were tested against a particle-filled (barium sulfate)
0.75 mil thick polyethylene microporous film. The microporous film had a
Gurley value of about 800 sec/50 cc (measured by ASTM-D-726-58, method A).
Results are given in Table IV.
TABLE IV
135.degree. Peel 135.degree. Peel
(2000 gm 135.degree. Peel (loose)
Ex. Tape rolldown) Shear (loose) w/oil
30 1 1808 764 315t 80
31 2 836
32 3 822 237t 234
33 4 503
34 5 931 367t 316t st
35 6 1001 426t 360 st
36 9 894 273t 191 st
t = tore, st = stretched
This film was extremely thin and generally tore when not contaminated with
oil and not reinforced (the 135.degree. loose peel with 100 gm rolldown).
However, the peel performance was generally excellent when contaminated
with oil, with the possible exception of Tape 1 (which tape also displayed
excessively high peels to this film when not contaminated).
Examples 37 and 38
A 1.7 mil oil-washed polypropylene microporous film (Example 37) and a 0.6
mil oil-washed polyethylene microporous film (Example 38) were prepared as
described in U.S. Pat. Nos. 4,539,256 and 4,726,989. The Example 37 film
originally had 35% mineral oil, and the Example 38 film originally had
about 70% mineral oil, and were washed with trichloroethylene to remove
the oil. Fastening tape 6 was tested against the washed films for
135.degree. peel adhesion and for oil-contamination tolerance. Results are
given in Table V. Example 38 tore.
TABLE V
135.degree. Peel 135.degree. Peel
(2000 gm 135.degree. Peel (loose)
Ex. Tape rolldown) (loose) w/oil
37 6 1075 901 788
38 6 1326 .sup. 49 t 275
t = tore
The oil contamination tolerance of these films was excellent.
Examples 39-42
Adhesive tapes having acrylate-based adhesives were tested against
oil-filled polypropylene microporous films (35% and 25% oil, film samples
A and C) for oil-contamination. The adhesive tape used for Examples 39 and
40 was Monta.TM. 391 (available from Monta of Germany) and the adhesive
tape used for Examples 41 and 42 was Scotch.TM. Magic.TM. Tape (No. 11257,
available from 3M Germany). Results are given in Table VI.
TABLE VI
135.degree. Peel
135.degree. Peel (100 gm
(100 gm rolldown,
rolldown, loose)
Ex. Porous Film loose) w/oil
39 A 159 66
40 C 297 155
41 A 338 204
42 C 456 262
Examples 43 and 44
A natural rubber-based adhesive tape (Y-9377 available from 3M) was tested
against oil-filled polypropylene microporous films (35% and 25% oil, film
samples A and C) for oil-contamination tolerance. Results are given in
Table VII.
TABLE VII
135.degree. Peel
135.degree. Peel (100 gm
(100 gm rolldown,
rolldown, loose)
Ex. Porous Film loose) w/oil
43 A 373 225
44 C 522 256
Comparative Examples 45-48
Fastening tapes 1 and 5 were tested against smooth biaxially oriented
polypropylene (BOPP) films, both with a low adhesion backsize (LAB)
coating (Examples C45 and C46) and without an LAB (Examples C47 and C48).
Results are given in Table VIII.
TABLE VIII
135.degree. Peel
135.degree. Peel (100 gm
135.degree. Peel (100 gm rolldown,
(2000 gm rolldown, loose)
Ex. Tape rolldown) Shear loose) w/oil
C45 1 168 823 46 9
C46 5 574 1082 323 46
C47 1 1975 1284 28
C48 5 1059 1400+ 786 99
Tape 5 exhibited some oil tolerance, however, peel performance was vastly
inferior to the peel performance of this tape against the oil-contaminated
microporous films. Tape 1 did not perform well against the
oil-contaminated non-porous films.
Comparative Examples 49-52
Fastening tapes 1, 5, 7 and 8 were tested against a conventional matte
polyethylene film typical of those that are used for disposable diaper
backsheets. Results are given in Table IX.
TABLE IX
135.degree. Peel
135.degree. Peel (100 gm
135.degree. Peel (100 gm rolldown,
(2000 gm rolldown, loose)
Ex. Tape rolldown) Shear loose) w/oil
C49 1 1352 400 435 12
C50 5 587 865 307 39
C51 7 707 165
C52 8 776 232
Tapes 7 and 8 have the ability to adequately adhere to these polyethylene
surfaces when contaminated with oil. However, the peels against the
contaminated surface are less than one-third the peel performance against
the non-contaminated surface. This limited oil-contamination tolerance is
due to the properties of the adhesive used on tapes 7 and 8. Peel
performance (contaminated vs. non-contaminated) was much more consistent
for the tape 7 and 8 adhesives when adhered against the microporous films.
Examples 53-68
Examples 53-68 (Table X) are adhesive tapes prepared by solvent coating the
adhesive composition onto a polypropylene film backing (4 mils). The
adhesive thickness for these tapes was about 32 microns. The adhesives
were all formed of elastomer with added solid tackifier.
The tapes were peel tested against a conventional matte polyethylene film
such as is used for a disposable diaper backsheet. All these tapes
exhibited some oil-contamination tolerance with the best peel performance
to oil-contaminated surfaces obtained with adhesives with at least 60
weight percent, preferably 65-85 weight percent, S-I diblock copolymer in
the elastomeric phase, having a percent styrene content of greater than 20
percent, preferably 22-26 percent, tackified with a solid C.sub.5
tackifier or a beta-pinene resin.
Generally, oil contamination tolerance (a peel of at least 30 N/m) to a
polyolefin surface, preferably polyethylene surfaces (with oil up to 0.12
mg/cm.sup.2) was observed for polystyrene-polyisoprene-based adhesives
where the elastomeric phase is greater than 40% diblock (the remainder
being triblock or other multi-block copolymers); the elastomer has a
percent styrene content of greater than 13 percent, preferably 15-30
percent; the solid tackifier compatible with the polyisoprene block is
used in amounts ranging from 30 to 200 parts, preferably 40-120 parts, per
100 parts elastomer; and no more than 15 percent, preferably less than 10
percent, of the adhesive composition is a liquid resin or plasticizing
oil. The solid tackifier is preferably a C.sub.5 resin, a C.sub.9 resin, a
beta-pinene resin or a rosin ester.
Generally, these oil-tolerant adhesives are preferred for use with the
oil-filled microporous film, oil-,contamination tolerant reinforcement
strips as these adhesives exhibit high peels to the oil-contaminated
surfaces, as well as not giving excessively high peels to the
non-oil-contaminated oil-filled microporous films. These tapes also have
the advantage of being able to adhere to oil-contaminated non-porous
polyethylene film, which is useful if the porous reinforcement strip is
missed.
These oil-tolerant adhesives adequately adhere to a polyethylene film,
particularly if the polyethylene film is reinforced on the inner face
opposite the outer face that the adhesive tape is attached to, such as by
a film plastic strip or tape.
TABLE X
135.degree. Peel
135.degree. Peel (100 gm
(100 gm rolldown,
% S-I Parts.sup.2 of rolldown, loose)
Example % Styrene Diblock.sup.1 solid resin loose) w/oil
53 15 40 70.sup.3 498 116
54 15 40 70.sup.4 577 142
55 15 55 70.sup.4 567 143
56 17 65 75.sup.5 618 158
57 17 79 70.sup.4 806 176
58 17 79 70.sup.6 718 167
59 17 79 70.sup.7 656 154
60 17 80 49.sup.5 699 175
61 19.6 65 75.sup.5 724 175
62 19.6 80 49.sup.5 710 189
63 22.6 65 75.sup.5 777 194
64 25.6 65 75.sup.5 786 187
65 22.6 80 49.sup.5 832 180
66 25.6 80 49.sup.5 784 204
67 22 70 70.sup.3 898 172
68 22 80 70.sup.6 825 177
.sup.1 Remainder of elastomer is essentially S-I-S triblock
.sup.2 Parts per 100 parts elastomer
.sup.3 Wingtack .TM. Plus (C5 resin from Goodyear Chemical Co.)
.sup.4 Piccolyte .TM. S-115 (beta-pinene based resin from Hercules Co.)
.sup.5 Wingtack .TM. 95 (C5 resin from Goodyear Chemical Co.)
.sup.6 Arkon .TM. P-115 (hydrogenated C9 resin from Arakawa Chemical)
.sup.7 Floral .TM. 85 (rosin ester available from Hercules Co.)
Example 69
Fastening tape 5 was tested against a porous heavily consolidated nonwoven
polyethylene web (Tyvek.TM. 1422R) having an effective pore size of 9
microns. The web was embossed on one face. Both faces were tested for 135
degree peel using the loose peel test described above, both with and
without oil contamination. The embossed face had peels of 131 gm/in and 72
gm/in for the non-oil-contaminated and oil-contaminated films,
respectively. The smooth face had peel adhesions of 81 and 31 gm/in,
respectively. These films displayed low peel values for the
non-contaminated peel test which would indicate the presence of a surface
treatment. However, the web did display oil-contamination tolerance
properties.
Example 70
A 9.5 in.times.6 in sample of the 25% oil film (porous film C) with print
was laminated onto an acrylate transfer adhesive and rolled over with a
4.5 lb roller. The transfer adhesive was made by pulling a 5-grains
coating weight handspread of an RD-975 (available from 3M) acrylate
adhesive on a release liner. A 9.5 in.times.2 in sample was then slit from
the laminate, which was then laminated onto the front of a Pampers.TM.
diaper. This sample was in turn rolled with a 4.5 lb roller to smooth out
any wrinkles. The resulting diaper had a functional contamination-tolerant
reinforcement strip.
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